Electromagnetic lockout switch



R. P; BOSSOM'.

ELECTROMAGNETIC LOCKOUT SWITCH.

APPLICATION FILED JULY23| 1918.

1,414,453. Patented May2, 1922.

.2 SHEETS-SHEET 1-.

R. P. BOSSOM.

ELECTROMAGNETIC LOCKOUT SWITCH.

APPLICATION FILED JULY 23. 1918.

1 414 453. Patented May 2, 1922.

2 SHEETS-SHEET 2.

mV/M

UNITED ROBERT PEEL BOSSOM, OF BRIGHTON, ENGLAND.

ELECTROMAGNETIC LOCKOUT SWITCH.

Specification of Letters Patent.

Patented May 2,1922.

Application filed July 23, 1918. SerialNo. 246,404.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. I, 1313.)

T 0 all whom it may concern:

Be it known that I, Bonner PEEL BossoM, a subject of the King of Great Britaln, and

resident of Brighton, Sussex, England, have cation. v p

This invention relates to electromagnetic lockout switches of the kind which have a shunt operating or closing coil and a series lockout or restraining coil so ar ranged in relation to a pivoted armature lever having closing and lockout armature's at its opposite ends .on either side of the pivot that the lookout coil operates to prevent closure of the switch under abnormal conditions, i. e. whenfthe current in the series coil is of too high a value.

Switches of this character as h narily constructed suffer from the disa-' bility that different voltages resultin the pull exerted by the shunt magnet fluctuat ing so that the switch cannot be relied upon to close at the desired current value under all conditions of voltage. The object of my present'invention is to provide an improved switch which will close at substantially the same currentvalue under all voltage conditions without entailing complicated con nections, and the primary feature of the invention consists in providing a second path for the magnetic flux of the shunt operating magnet, this second path being so disposed that the flux flowing through it tends to assist the series coil to hold the switch open in opposition to the. closing pull resulting from the magnetic flux flow ing through the other path. .That is to say, there are two magnetic forces acting cumulatively at one end of the pivoted armature lever to hold the switch open, i. e.

the magnetic force due to the series lockout coil and the magnetic force due to that portion of the flux of the operating or closing coil which flows through the magnetic circuit of the, series lockout coil, while the other end of the pivoted armature lever is subjected to an opposing force.

It will be understood that the proportions of the flux flowin through either of the two paths aforesaid will depend upon the ithe'r'to ordirespective reluctances of the two magnetic c rcuits, and by a suitable arrangement and di position of the iron parts and air gaps of: these magnetic circuits the pull due to one portion of the flux can be regulated relative to the other so that either-may be made to predominate or they may be made equal. Bymeans ofthe foregoing, fluctuations'of the pull of the shunt closing magnet due to voltage variations will be compensated for by fluctuations in the pull of the lookout magnet. For instance,upon an in crease of voltage the pull of the shunt holding oroperating magnet will increase;

but it will be accompanied by a corresponding increase in the pull of the holding or lockout magnet. The armature proper adapted to be attracted by the lookout mag net is mounted onthefpivoted armature.

lever spring and so arranged that when the lockout armature is attracted the spring tends to oppose the pull of the" lockout mage net andm some caseswe propose to provide the lockout magnet with an additional shunt coil as will hereafter more fully appear.

Another feature of the inventionof great practical importance is the construction whereby an ordinary contactor switch can be converted into a lookout switch by the application to it of the looking out magnet and its armature.

In the accompanying drawings I have illustrated my invention, Fig. 1 being a more or less diagrammatic side elevational view of the operative parts of a switch constructed in accordance with the invention.

Fig. 2 is a view of a complete switch which although slightly difii'erent indetail of construction involves precisely similar essential parts and operates in precisely the same p'rinciple'as that shown in Fig 1.

Fig. 3 a view illustrating a modification.

Referring to these drawings the switch takes the form of an ordinary contactor having an armature a carried by a pivoted lever 9 with an ordinary shunt closing or operating coil b surrounding the core 6 This closing or operating coil b is mounted upon 'a frame 0 of magnetic material carried by the usual insulating panel 05, this magnet frame 0 having an extension 0 upon which a series coil 6 is mounted, the two coils b and ebeing arranged upon opposite sides of the pivotal point of the lever g so that the n'iagnetic forces act oppositely upon the pivoted armature lever. By reason of the extension (,9 aforesaid of the magnet frame, the magnetic flux set up by the shunt coil. has two paths, and in operation the flux produced by this shunt holding or closing coil Z) is divided into two portions one of which takes the path of the ordinary contactor from the magnet core 71 to the magnetic frame or base 0 and back to the magnet core by way of the main armature a in the usual way. This may be regarded as the closing magnetic circuit. .The other portion of the flux passes from the magnet core 6- to the magnetic frame or base 0 as before and thence passes by way of the extension aforesaid of the magnet frame through the magnetic circuit of the series lockout coil 0. This may be regarded as the lockout magnetic circuit. The coil 6 is support (d upon core c held to the member 0 by a stud e the ends of the coil, being connected to screw terminals 0" and e" screwed into ports (2 and 0" attached to the panel Therefore, the one portion of the flux of the shunt closing or operating coil 6 passes through the closing magnetic circuit and tends to effect closure of the switch, and the other portion passes through the lock out magnetic circuit and tends to hold the switch open. It will be clear from the foregoing that any increase in flux due to an alteration in the voltage of the current in the shunt coil Z) will result in an alteration of the flux in both the paths, and it will be found that variations of voltage impressed upon the shunt coil aforesaid will not affect the relative pulls exerted by the two flux portions.

In order to make the switch operate as a lookout switch for use with a motor starter, I provide a series coil 6 in the lockout circuit as before indicated, and the flux produced by this series coil, 0 acts cumulatively with that portion of the flux of the shunt closing or operating magnet which tends to restrain closure of the switch. The armature g in the locking out magnetic circuit is carried upon the free end of a leaf spring 9'' rigidly secured at its other end to the block carried by the bracket which in turn is rigidly secured by the studs or bolts 9 to the lever g carrying the armature a of the closing magnet. Thus the le ver 9 carrying the armature a and the bracket g carrying the armature constitute a rigid structure adapted to rock about the pivotal point 7' and referred to herein as the pivoted armature lever. This bracket g is of magnetic material and forms part of the locking out magnetic circuit. The tendency of the spring g when the armature g is attracted is to oppose the lockout pull. By means of a screw or other adjusting device and a locking nut ,7 the air gap between the lookout armature g and the lookout magnet 0 can be regulated so that the current value at which the switch will close can be set or regulated. The lockout armature 9' passes through an opening 9 in the bracket and, is provided with a stop g to regulate the position of the lockout armature relative to the pole ofthe lock out magnet when the armature is in at tracted position. The operation. of the switch is as follows: Assuming that the series coil 6 is in the motor circuit, and a series of these switches are being used to control resistances in the motor circuit, upon closure of a switch the shunt closing or operating coil 6 is energized, and tends to close the switch, but closure is opposed by the effect of the series coil 0, which owing to the peak in the motor circuit attracts the lookout armature to the fullest extent permitted by the stop 9 and holds it there until the motor current has fallen to a certain predetermined value. At this point the pull upon the main shunt armature g is able to overcome the combined pull of the series coil 0 and the pull due to the locking out portion of the flux of the shunt coil 7). Thus the armature 9 will be released and the springg will carry it away rapidly and the switch will close and in so doing energize the next switch of the series which will. 01)- erate in similar manner as will be readily understood by those conversant with lockout switches.

It is not always desirable to rely upon the peak of the motor current to attract the lockout armature to closed position, and for this reason it may be arranged to have a shunt lockout coil 71 (see Fig. 3) to attract the lockout armature initially, a suitable means as indicated in the diagram, Fig. A, being provided for cutting this shunt lockout coil out of circuit after it has fulfilled its function of pulling in the lookout armature. Moreover, I may arrange some of the switches of a series with double series lockout coils and provide suitable means for cutting out a part of each coil when it is desired to have the switch operating as a lockout. That is to say, closure of a preceding switch will result in half the series coil of the next lockout switch being cut out. Thus the switch will operate eifectively without relying on peak currents at all since the arrangement can be such that the lockout armature will be attracted initially even when the motor current is under normal value. After the lockout armature has been attracted, the forces tending to hold the switch open are as aforesaid the forces exerted by the series coil 6 and a portion of the flux of the shunt closing or operating coil, and the forces tending to close the switch is the force exerted by the other portion of the flux of the closing or operating magnet.

The cumulative effect of the former predominates at high current values and the switch remains open, but when the current in the series lockout coil falls to a safe value the latter force predominates and the switch closes as a consequence. It will be seen upon reference to the drawings that to convert an ordinary contactor into a lockout switch only requires the application to the insulating paneld of the extension 0 of magnetic material which carries the locking out coils and the application to the main armature g of the bracket g by means of the studs or bolts 9 and this will be found an important advantage.

What I claim and desire to secure by Letters Patent is:

An electromagnetic lockout switch comprisingla magnet frame, a pivoted armature lever, mounted on said frame, a shunt holding or closing coil, a series lockout coil, armatures aving a rigid extension on one end, a

for said coils, a spring mounted on said rigid extension and carrying the armature for the lockout coil thereon, the other armature being mounted upon the opposite end of the pivoted armature lever which con sists essentially of a rigid structure adapted to rock on a pivot, cores for said coils mounted on the magnet frame and in the magnetic flux path, the magnetic system being such that a portion of the magnetic flux generated by the closing coil passes to the magnetic circuit of the looking out coil and acts cumulatively with the magnetic flux generated by the looking out coil whereby fluctuations in the pull upon the pivoted armature lever exerted by the closing coil due to voltage variations are accompanied by corresponding fluctuations of the lockin out pull.

n testimony whereof I aflix my signature.

ROBERT PEEL BOSSOM. 

